CN106238727A - A kind of preparation method of Cu bag W composite granule - Google Patents

Abstract

The invention discloses a preparation method of Cu-wrapped W composite powder, which uses W powder and soluble copper salt as raw materials, dissolves the copper salt in water, and adds ammonia water to prepare an aqueous copper ammonia complex solution; then adds W powder to form A multi-phase mixed solution in which W powder is in suspension; the mixed solution is dispersed under the joint action of electric stirring and ultrasonic waves, and heated to 70-80°C for ammonia reduction, centrifugal precipitation, washing and drying, and finally Cu-coated W is obtained Composite powder. The preparation method of the Cu-coated W composite powder of the present invention does not require the reduction process of tungsten-copper oxide in the conventional preparation method, the preparation process is simplified, and the preparation cost is low. The obtained coating powder has a core-shell structure, W-Cu composition The powder is evenly distributed; and the powder has good compaction properties, which is conducive to the preparation of high-performance W-Cu composite materials with uniform components.

Description

A kind of preparation method of Cu-wrapped W composite powder

technical field

The invention belongs to the field of powder material preparation, and in particular relates to a preparation method of Cu-wrapped W composite powder.

Background technique

W-Cu composite material is a pseudo-alloy composed of two immiscible metal phases. Therefore, the composite material combines the high melting point, high hardness, low linear expansion coefficient of tungsten and the high electrical conductivity and high thermal conductivity of copper, and is widely used as a function and structure of electrical contactors, vacuum circuit breakers, heat sink materials, etc. device. At present, the preparation of W-Cu composite materials mainly relies on infiltration method and high temperature liquid phase sintering method. Due to the high hardness and poor formability of tungsten powder, it is difficult to obtain the skeletal density required for high-tungsten-content W-Cu materials at general high temperatures, and it is difficult to prepare high-density high-tungsten-content W-Cu materials by immersion method. Affected by the incompatibility and low wettability between W and Cu, conventional high-temperature liquid phase sintering cannot obtain W-Cu materials with uniform structure, high density and high tungsten content. In order to improve the density of composite materials, complex post-processing (such as repressing, refiring and hot pressing) is usually performed on alloy materials, which not only increases the production cost, but also increases the complexity of the preparation process. .

In order to further improve the sintering activity of W-Cu composites, expand the application of W-Cu composites. Ultrafine composite powder has become a new method for preparing high-performance W-Cu composite materials in recent years. Due to the advantages of fine grain size, high surface activity and good sintering driving force, the ultrafine W-Cu composite powder can greatly reduce the sintering temperature, promote particle rearrangement, and greatly increase the density of the sintered body, thereby improving Comprehensive properties of composite materials. At present, the methods for preparing ultrafine composite powder mainly include mechanical and chemical methods, such as mechanical thermochemical method, spray drying method and sol-gel method. For example, Li Junqiang et al. used _CuO and WO3 as raw materials to prepare tungsten-coated copper nanocomposite powders through high-energy ball milling and hydrogen reduction at 360°C and 750°C (Junqiang L, Wenge C, Wenjun T, et al. Nano-composite powder oftungsten coated copper produced by thermo-chemistry co-reduction [J]. Rare Metal Materials and Engineering, 2012, 41(12): 2091-2094). However, impurities are easily introduced into the W-Cu composite powder prepared above, and a two-stage hydrogen reduction process is required, and the process is complicated. The spray drying method is also called the thermochemical synthesis method, and its preparation process includes three stages of original solution preparation and mixing, spray drying and fluidized bed conversion. Su Weifeng et al. obtained ultrafine W-Cu composite powders with components of W-10% Cu, W-15% Cu and W-20% Cu by spray drying-hydrogen reduction method (Su Weifeng, Xiong Ning, Zhou Wuping, etc. 1 A new process for preparing W-Cu composite materials [J]. Powder Metallurgy Materials Science and Engineering, 2007,12(6):369-373). The spray drying method is suitable for mass production, the process control is simple, and it is not easy to introduce other impurity elements, but it is more important to control the reduction process of the powder precursor.

For the W-Cu system whose sintering densification mechanism is dominated by particle rearrangement, the homogenization of raw powder components can significantly improve its sintering performance. Coating a layer of Cu uniformly on the surface of W powder can avoid direct contact between W and W, promote the uniform distribution of composite powder components, reduce component segregation, strengthen the matrix interface, and finally improve the comprehensive performance of composite materials. For example, Lianmeng Zhang et al. used electroless plating to prepare W-Cu composite powder with a uniform coating structure, and the density of the sintered body was as high as 98.4% (Lianmeng Zhang, Wenshu Chen, Guoqiang Luo, et al.Low-temperature densification and excellent thermal properties of W– Cu thermal-management composites prepared from copper-coated tungsten powders [J]. Journal of Alloys and Compounds, 2014, 588: 49-52.). However, the electroless copper plating process is complicated, and the reducing agent used has serious pollution to the environment.

Contents of the invention

In order to solve the shortcomings of the above-mentioned prior art, the present invention provides a method for preparing Cu-wrapped composite powder, which aims to avoid the reduction process of tungsten copper oxide in the conventional preparation method, simplify the preparation process and reduce the preparation cost.

The preparation method of the Cu-wrapped W composite powder provided by the present invention can be referred to as the "ammonia distillation reduction precipitation" method.

The so-called ammonia distillation reduction is to use W powder and soluble copper salt as raw materials. The raw material copper salt is dissolved in water and ammonia water to form a copper ammonia complex aqueous solution, and the raw material W powder is added to form a multiphase mixed solution. The multiphase mixed solution is heated at a certain temperature. Under heating to distill ammonia. During the heating process of ammonia distillation, Cu ²⁺ in the mixed liquid is used as an oxidant to be directly reduced to Cu simple substance, and W powder is partially oxidized to W ⁶⁺ to form tungstate.

The present invention adopts following technical scheme for solving technical problems:

The preparation method of Cu-wrapped W composite powder of the present invention is characterized in that it is carried out according to the following steps:

a. Using ultrafine W powder and soluble copper salt as raw materials, dissolve the soluble copper salt in water, add ammonia water to form an aqueous solution of copper ammonium complex, and then add ultrafine W powder to form a multiphase mixed solution in which W powder is in suspension ;

b, heating the multiphase mixed solution to distill ammonia;

c. Centrifuge the mixed solution after ammonia distillation, wash and dry the obtained precipitate, and obtain Cu-coated W composite powder.

The preparation method of the Cu-wrapped W composite powder of the present invention is also characterized in that:

The superfine W powder in step a is a commercial W powder with a particle size of ≤0.8 μm, and the soluble copper salt is copper nitrate or copper sulfate.

The proportion of W powder and soluble copper salt is calculated based on W and Cu elements, and is based on the Cu content in the Cu-wrapped W composite powder; Loss amount; the molar ratio of W powder loss to Cu element is 1:3.

The copper ammonia complex in step a exists in the form of Cu(NH ₃ ) ₄ ²⁺ , the amount of ammonia water added is based on Cu ²⁺ , and the molar ratio of Cu ²⁺ to NH ₃ is 1:8.

The process of distilling ammonia by heating in step b is: dispersing the multi-phase mixed solution formed by copper ammonia complex aqueous solution and W powder under the joint action of electric stirring and ultrasonic waves, and heating to 70-80°C to distill ammonia, until the pH of the solution reaches neutral.

Preferably, the rotational speed of the electric stirring and dispersing is 300-400r/min.

Preferably, the ultrasonic dispersion frequency is 40KHz, and the power is 300-400W.

The washing described in step c is to add deionized water to wash, and repeat it several times.

The drying described in step c is to dry to constant weight at 60° C. in a blast drying oven.

The W-Cu composite powder obtained in the present invention can obtain a high-density sintered body (composite material) through conventional forming and sintering processes. After sintering at lower than 1400°C, the relative density of the obtained sintered body is higher than 97%, and the grain size is 1-1.8 μm.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

The present invention is based on the principle of redox, and directly obtains Cu-wrapped W composite powder by heating and distilling ammonia in a multi-phase mixed solution of copper ammonium complex solution and W powder. The preparation method of the Cu-coated W composite powder of the present invention has a simple process, especially does not require the reduction process of tungsten copper oxide in the conventional preparation method, and the preparation cost is relatively low. The obtained coating powder has a core-shell structure, W-Cu The components are evenly distributed. The powder has good compaction performance, which is conducive to the preparation of high-performance W-Cu composite materials with uniform components.

Description of drawings

Fig. 1 is the process flow diagram of preparing Cu-wrapped W composite powder in the present invention;

Fig. 2 is the X-diffraction analysis result of the W-Cu composite powder prepared in Example 1 of the present invention;

Fig. 3 is the SEM photo of the W-Cu composite powder prepared in Example 1 of the present invention;

Fig. 4 is the SEM photo of the section of the W-Cu sintered body prepared by the W-Cu composite powder of Example 1 of the present invention;

Fig. 5 is the X-diffraction analysis result of the W-Cu composite powder prepared in Example 2 of the present invention;

Fig. 6 is a TEM photo of the W-Cu composite powder prepared in Example 2 of the present invention.

detailed description

Example 1

As shown in Figure 1, this embodiment prepares Cu-wrapped W composite powder according to the following steps:

Dissolve 7.56g of copper nitrate trihydrate in 100mL of deionized water, and add ammonia water with a concentration of 25% according to the molar ratio of Cu2 ⁺ and _NH3 of 1:8 to form an aqueous copper ammonia complex solution. Weigh 20 g of W powder with an average particle size of about 0.8 μm and add it to the cupro-ammonia complex aqueous solution to prepare a 500 mL multiphase mixed solution. The multi-phase mixed solution is placed in an ultrasonic cleaner and dispersed under the joint action of ultrasonic waves and electric agitation, wherein the ultrasonic dispersion frequency is 40KHz, the power is 300-400W, and the rotational speed of electric agitation is 300-400r/min. At the same time, heat to 80°C to distill ammonia until the pH of the mixture drops to neutral, and the reaction ends.

The precipitate was washed with deionized water several times, centrifuged and precipitated, and then dehydrated and dried to a constant weight at 60°C in a blast drying oven to obtain a W-Cu composite powder. The mass percentage of Cu in the obtained composite powder was 10%.

Fig. 2 is the X-diffraction analysis result of the W-Cu composite powder prepared in this embodiment, it can be seen from the figure that only the characteristic peaks of W and Cu appear in the composite powder, indicating that after the ammonia distillation reaction, it can be directly Obtaining W-Cu composite powder does not require the reduction process of tungsten copper oxide in conventional preparation methods.

Fig. 3 is the SEM photograph of the W-Cu composite powder prepared in this example, it can be seen from the figure that the prepared powder is evenly distributed; Coated on the surface of W powder.

The W-Cu composite powder prepared in this example is conventionally pressed and sintered in liquid phase at 1250°C to obtain a W-Cu sintered body. The SEM photo of its cross-section is shown in Figure 4, from which it can be seen that Cu The phases are evenly distributed between the WW phases, forming a certain continuous and tight network structure; after testing, the sintered density is 16.98g/cm ^-3 (relative density 98.15%), and the grain size is 1-1.8μm.

Example 2

As shown in Figure 1, this embodiment prepares Cu-wrapped W composite powder according to the following steps:

Dissolve 7.81g of copper sulfate pentahydrate in 100mL of deionized water, and add ammonia water with a concentration of 25% according to the molar ratio of Cu2 ⁺ and _NH3 of 1:8 to form an aqueous solution of copper ammonia complex. Weigh 20 g of W powder with an average particle size of about 0.5 μm and add it to the cuproammonia complex aqueous solution to prepare a 500 mL multiphase mixed solution. The multi-phase mixed solution is placed in an ultrasonic cleaner, and dispersed under the joint action of ultrasonic waves and electric stirring, wherein the ultrasonic dispersion frequency is 40KHz, the power is 300-400W, and the rotational speed of electric stirring dispersion is 300-400r/min. At the same time, heat to 80°C to distill ammonia until the pH of the mixture drops to neutral, and the reaction ends. The precipitate was washed with deionized water several times, centrifuged and precipitated, and then dehydrated and dried to a constant weight at 60°C in a blast drying oven to obtain a W-Cu composite powder. The mass percentage of Cu in the obtained composite powder was 10%.

Fig. 5 is the X-diffraction analysis result of the W-Cu composite powder prepared in this embodiment, as can be seen from the figure, only the characteristic peaks of W and Cu appear in the composite powder, indicating that copper sulfate pentahydrate is used as copper source, W-Cu composite powder can also be obtained after ammonia distillation.

FIG. 6 is a TEM photo of the W-Cu composite powder prepared in this example. It can be seen from the figure that a certain amount of Cu is covered on the surface of the W powder.

The W-Cu composite powder prepared in this example was pressed and sintered in the same manner as in Example 1 to obtain a W-Cu sintered body with a sintered density of 16.83g/cm ^-3 (relative density 97.39%), The grain size is 0.8-1.2μm, which has good comprehensive performance.

Claims (6)

1. the preparation method of a Cu bag W composite granule, it is characterised in that carry out as follows:

A, with ultra-fine W powder and soluble copper salt as raw material, soluble copper salt is soluble in water, add ammonia and form cupric ammine complex Aqueous solution, adds ultra-fine W powder, forms W powder and is in the heterogeneous mixed solution of suspended state；

B, by heterogeneous mixed solution heat ammonia still process；

C, the mixed solution after ammonia still process is centrifuged, to gained washing of precipitate, is dried, i.e. obtain Cu bag W composite granule.

The preparation method of Cu bag W composite granule the most according to claim 1, it is characterised in that: ultra-fine W powder described in step a For the business W powder of granularity≤0.8 μm, described soluble copper salt is copper nitrate or copper sulfate.

The preparation method of Cu bag W composite granule the most according to claim 1, it is characterised in that: W powder and soluble copper salt Proportioning calculates with W and Cu element, is as the criterion finally meeting Cu content in Cu bag W composite granule；W powder addition is for comparing institute by metering Requirement and W powder are because of the oxidized waste caused；The waste of W powder is 1:3 with the mol ratio of Cu element.

The preparation method of Cu bag W composite granule the most according to claim 1, it is characterised in that: copper ammonia complexation described in step a Thing is with Cu (NH₃)₄ ²⁺Form exists, and ammonia addition is with Cu²⁺It is as the criterion, Cu²⁺With NH₃Mol ratio be 1:8.

The preparation method of Cu bag W composite granule the most according to claim 1, it is characterised in that: heat ammonia still process described in step b Process be: heterogeneous mixed solution cupric ammine complex aqueous solution and W powder formed is at electric stirring and the common work of ultrasound wave Disperse under with, and be heated to 70-80 DEG C and carry out ammonia still process, until solution ph reaches neutral.

The preparation method of Cu bag W composite granule the most according to claim 1, it is characterised in that: described in step c be dried be Air dry oven is dried to constant weight at 60 DEG C.